The major phenolics of PrunellaL. species were isolated, and antioxidant activites were determined by 2,2-azino-di-(3-ethylbenzothialozine-sulphonic acid). The isolated compounds were identified as rutin, rosmarinic acid and caffeic acid by high performance liquid chromatography-diode array detection. The results show that the phenolic compounds were isolated from PrunellaL. species with high content ranged from 74% (Prunella grandifloraL.) to 99% (Prunella orientalisBornm.), and the major compound of rosmarinic acid was isolated above 90% in all species. Antigrowth effects of PrunellaL. species were tested against human breast cancer cell lines, MCF-7 (estrogen receptor-positive) and MDAMB-231 (estrogen receptor-negative) by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) and ATP (adenosine triphosphate) viability assays. To determine the mode of cell death, M30-antigen assay was performed in order to measure apoptosis. It was found that Prunella laciniata (L.) L., P.orientalisBornm. and P.grandifloraL. species showed antigrowth effect on MCF-7 and MDA-MB-231 breast cancer cells, but apoptosis was not observed. Practical ApplicationsFour PrunellaL. species (Prunella vulgarisL., Prunella laciniataL., Prunella grandifloraL. and Prunella orientalisBornm.) have been used in Western and Chinese herbal medicine that possesses antioxidant properties. PrunellaL. species have a broad chemical composition, consisting of bioactive molecules as phenolic acids, flavonoids and anthocyanidins. It was found that PrunellaL. species showed a significant growth-inhibiting effect on human breast cancer cells, but apoptosis was not involved in cell death. The results suggest that the isolated rutin and rosmarinic acid, as the principal components of PrunellaL. extracts, could be utilized as both medicine and herbal tea.